Preparation of glass for radiotherapy of cancer by P + ion implantation at 100 keV

Abstract

A chemically durable glass containing a large amount of phosphorus is useful for in-situ irradiation of cancers. It can be activated to be a β-emitter with 14.3 days half-life by neutron bombardment. Microspheres of the activated glass injected into the tumors can irradiate the tumors directly with β-rays without irradiating neighboring normal tissues. In the present study, a P + ion was implanted at 100 keV. There was little phosphorus present in the surface region, at least to a depth of 2.4 nm for doses of 5×10 16 and 1×10 17 cm −2, whereas an appreciable amount of it was distributed on to the glass surface and a part of it was oxidized for doses above 5×10 17 cm −2. The glasses implanted with doses of 5×10 16 and 1×10 17 cm −2 released little both of the P and Si into water at 95°C, even after 7 days, whereas the glasses implanted to doses above 5×10 17 cm −2 released appreciable amounts of these elements. At implantation energy of 20 and 50 keV, even doses of 5×10 16 and 1×10 17 cm −2, respectively, formed oxidized phosphorus on the glass surfaces and gave appreciable releases of the P and Si into the hot water. This indicates that a chemically durable glass containing a larger amount of phosphorus could be obtained if P + ion implanted at higher energies is localized in a deeper region.